Assessment of the development and disappearance of the open-air markets in Montreal. The author traces the history of this phenomenum, using a lot of pictures and archival movies, and more actual documents as well to put a light on these places of communication. Born in the XVIIe century, the open-air market has known a great expansion, then it will lose its original vocation before disappearing for the most of them. The video offers in parallel a reflection about the architectural heritage of Montreal, in a didactic approach.